I stopped having issues. Hope this fix before helps someone.
I have a laptop with RTX 3070 mobile on Windows 11.
I did a clean install of Unreal. 4.27.1,
I upgraded Nvidia driver 496.49.
In Unreal 4 → Editor Preferences → Appearance → I unchecked “Show Window Animations”.
In Unreal 4 → Editor Preferences → Appearance → i unchecked “Use Small Toolbar Icons”.